<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form id="uploadForm" action="${ctxPath}/video/upload" method="post" enctype="multipart/form-data">
    <input type="submit" value="提交">
    <button type="button" id="add">增行</button><br>
    <input type="file" name="file"><br>

</form>

</body>
</html>
<script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.js"></script>
<script type="text/javascript">
    $(function () {
        $('#add').click(function (ev) {
            var $form = $("#uploadForm");
            var name = 'file' + new Date().getTime();
            var $newInput = "<input type='file' name='"+ name +"'><br>";
            $form.append($newInput);
            console.log($form)
        })
    })
</script>